Nitrile-Coated Olivine Cathode Particles for Stable Battery Capacity
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing secondary batteries have insufficient battery characteristics, necessitating improvements to achieve better performance.
Innovation Solution
A positive electrode for a secondary battery is designed with a positive electrode active material layer containing olivine-type phosphate compound particles. Each particle has a central part with a granulated structure and a covering part containing a nitrile group, optimizing the manganese and iron content, particle diameters, and porosity to enhance electron conductivity and stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the particle size of the positive electrode active material is increased to improve electron conductivity, then the electron conductivity is improved, but the battery capacity and operation stability deteriorate
Solution Approach 1:
The positive electrode active material particles are divided into primary particles (0.01-0.5 μm) that are granulated to form secondary particles (1-20 μm). This segmentation allows the fine primary particles to provide high surface area for lithium insertion/extraction while the granulated secondary particles provide good electron conductivity and structural stability, resolving the contradiction between conductivity and capacity.
Solution Approach 2:
The positive electrode active material particles consist of a core-shell composite structure where the core contains the olivine-type phosphate compound and the shell contains a nitrile group. This composite structure combines the high capacity of the olivine core with the protective and conductive properties of the nitrile shell, achieving both high battery capacity and stable operation.
2Quantity of substance
If the porosity of the positive electrode active material layer is increased to improve electrolyte penetration, then the battery capacity is improved, but the mechanical strength and physical durability deteriorate
Solution Approach 1:
The nitrile group shell is selectively formed on the surface of the positive electrode active material particles, providing local protection and structural integrity. This localized modification allows the interior particles to maintain high porosity for electrolyte penetration while the outer shell provides mechanical strength, resolving the contradiction between capacity and durability.
3Quantity of substance
If the manganese content in the olivine-type phosphate compound is increased to improve battery capacity, then the battery capacity is improved, but the structural stability and operation potential stability deteriorate
Solution Approach 1:
The manganese content in the olivine-type phosphate compound is optimized to 50-90 parts by mole, balancing the capacity enhancement from higher manganese content with the structural stability provided by iron. This parameter optimization, combined with the nitrile group shell, achieves both high capacity and stable operation potential.
Data Source
AI summary
A secondary battery is provided and includes a positive electrode including a positive electrode active material layer, a negative electrode, and an electrolytic solution. The positive electrode active material layer contains a plurality of positive electrode active material particles, and each of the plurality of positive electrode active material particles includes a central part containing an olivine-type phosphate compound and a covering part provided on a surface of the central part. The olivine-type phosphate compound contains manganese and iron as constituent elements, and when a sum of a content of the manganese in the olivine-type phosphate compound and a content of the iron in the olivine-type phosphate compound is 100 parts by mole, the content of the manganese in the olivine-type phosphate compound is 50 parts by mole or more and 90 parts by mole or less. The central part is a secondary particle formed by granulating a plurality of primary particles, a first median diameter relating to the plurality of primary particles is 0.01 μm or more and 0.5 μm or less, and a second median diameter relating to the plurality of secondary particles is 1 μm or more and 20 μm or less. The covering part contains a nitrile group. The positive electrode active material layer has a porosity of 20% or more and 40% or less.